The invention relates to a novel type of internal for installation inside a chamber, particularly cylindrical, which can be rapidly assembled and disassembled, without welding, and without screws or clamping bolts.
The invention relates more particularly to a distribution tray for a fixed catalyst bed chemical reactor, fed with a gas/liquid mixture and preferably operating in cocurrent downflow.
This is the application referred to below in the rest of the present description, but the internal of the invention can be installed in all sorts of large-sized chambers, used in the chemical or petroleum industry or elsewhere, in which it is necessary, for example, to install a separation platform or a tray, perforated or not, serving for example for the distribution of a liquid or as a support tray for any type of filler or packing.
In fixed catalyst bed chemical reactors, traversed by a mixed downflow consisting of a gas phase and a liquid phase, the fine dispersion of said liquid phase in the gas phase and the uniform distribution of the mixture obtained over the entire surface of the catalyst bed, constituting the reaction zone, are commonly obtained by means of substantially horizontal perforated trays called “distribution trays”. For this purpose, these trays are generally formed from a single plate or a set of juxtaposed, welded, screwed or bolted plates, having a total area substantially identical to the area of the reactor cross section, generally cylindrical. Each plate comprises a large number of perforations each surrounded by a vertical cylindrical wall (called “riser” in the art) comprising, at its base, one or more holes or slits. These distribution trays, equipped with risers, operate according to the following principle: the gas introduced under pressure at the top of the reactor passes through the perforations surrounded by the risers. The liquid, also introduced at the top of the chamber, is retained on the plate from which it cannot flow freely due to the damming action of the risers. The liquid rises to a level identical to that of the height of the holes at the base of the risers and flows through them into the openings of the risers, where it is dispersed in fine droplets, being propelled by the gas stream.
Caps, or circular or rocker-shaped valves, can replace the abovementioned risers, particularly in trays used as elements for increasing the impingement area between the gas and the liquid in distillation columns, for example, crude oil distillation columns. Also found in the art are perforated downcomer trays, in which the gas passes through simple perforations distributed in the plates forming the active area of said trays.
The present invention relates not to the various types of elements for retaining, mixing or dispersing the liquid phase, but to a system for assembling and fixing plates constituting the tray in the reactor. This assembly and fixing system, as described below, is consequently not limited to a particular type of plate or use, but applies to any type of tray to be installed and, if necessary, rapidly disassembled, in any type of chamber.
Various distribution trays for chemical reactors have been proposed in the art and are described, for example, in FR 2 745 202, EP 768 914, EP 1 147 809, U.S. Pat. No. 3,524,731 or U.S. Pat. No. 5,882,610. Some of these trays are of the single-plate type, with a self-supporting structure, and are factory mounted inside the reactor. Others consist of several elements fixed to one another, and to holding beams, by screws or bolts, as indicated in U.S. Pat. No. 5,192,465 or U.S. Pat. No. 6,267,359. Such a screwing or bolting system has many drawbacks, and particularly that of the high cost of procuring the screws or bolts, particularly when the area of the distribution tray may be as high as about 10 square meters. A further drawback associated with this fixing system is to make the assembly and, above all, the disassembly thereof, whether partial or total, in the reactor, time-consuming and difficult, for example, in case of renewal of the catalyst bed. Furthermore, the personnel in charge of these operations must be protected against potentially toxic waste vapors by protective clothing, which severely limits their mobility and agility in handling tools such as wrenches or screwdrivers. All these drawbacks associated with lengthy and difficult handling operations ultimately imply prolonged reactor down time, which is detrimental to operating profitability.
Moreover, to guarantee undisturbed operation and also uniform distribution of the gas/liquid mixture at the surface of the catalyst bed, a distribution tray must be flat and horizontal and as tight as possible at the junctions between its various elements.
In the course of its research aimed at improving the structure of distribution trays and at facilitating their installation in reactors, the Applicant has developed a novel type of tray that is at once solid, tight at the junctions between the plates constituting it, and easy to assemble or disassemble. This tray consists of a set of plates some of whose edges are made up of female or male parts, capable of nesting respectively in the matching male or female parts of the adjacent plates, in order to form rows of juxtaposed plates fixed to one another without the need for screws or bolts. In this reactor, these rows of plates, which must be perforated for this specific type of use, are supported by beams fixed by their ends to the reactor walls, to which they are connected by a system without screws or bolts.